Heat a medium pot over medium-low heat. Add the olive oil followed by the minced garlic and ginger. Cook for a minute, until fragrant. Add in the sweet potatoes followed by 2 cups of broth. Cover and let the sweet potatoes cook until really tender; 10 to 15 minutes (depending on how large your cubes are). 

Transfer the cooked sweet potatoes and liquid to a blender then add in the soy sauce and puree until smooth, adding more broth as needed. Transfer the sweet potato mixture back to the pan and add even more broth until the sweet potatoes resemble a thin soup. 

Bring the liquid to a simmer and add the noodles. Cook, stirring often until the noodles are cooked. Stir in the miso and add more liquid if the noodles soaked up too much. The liquid should still be almost-broth consistency. Taste and adjust seasonings as desired. 

Divide the ramen into two large bowls. Top with eggs, arugula, and toasted sesame seeds.